Drugs may be delivered to patients by a variety of methods including oral, intravenous, intramuscular, inhalation, topical or subcutaneous delivery. The drug may be delivered directly or locally to the treatment site (e.g., intrathecally, intraspinally, intraarticularly, etc.). The method of delivery chosen depends upon, among other things, the condition being treated, and the desired therapeutic concentration of the drug to be achieved in the patient and the duration of drug concentration that must be maintained.
Drug pellets, such as, for example, drug depots have been developed, which allow a drug to be introduced or administered to sites beneath the skin of a patient. The drug depot releases the drug over a period of time. Drug depots allow the drug to be released from the depot in a relatively uniform dose over weeks, months or even years. Administering drugs using drug depots is becoming especially important and popular in modulating the immune, inflammation and/or pain responses in treatment of chronic conditions including rheumatoid arthritis, osteoarthritis, sciatica, carpal tunnel syndrome, lower back pain, lower extremity pain, upper extremity pain, cancer, tissue pain and pain associated with injury or repair of cervical, thoracic, and/or lumbar vertebrae or intervertebral discs, rotator cuff, articular joint, TMJ, tendons, ligaments, muscles, and the like.
Drug delivery devices have been developed to implant drug depots within a patient. These devices have a cartridge that contains one or more drug depots. A rod is moved within the cartridge to push the drug depot out of the cartridge. However, the drug depots can be misdirected as they are pushed through the cartridge by the rod. In some cases, the drug depots have the potential to lift and escape a pathway of the cartridge, thus preventing the drug depots from being properly expelled from the cartridge or, in some cases, from being expelled at all. This disclosure describes improvements over these prior art technologies.